Vendor

"Hi ____,

Thank you so much for meeting with me to discuss my wedding next year. Unfortunately, we have decided to go a different direction.

Respectfully,

(Your name)"

Should be all they need, and I'm sure they'll appreciate you letting them know so they don't continue to follow up.

Don't feel bad! They're used to it if you inform them you've decided to go in a different direction

No need to feel bad - this is part of their business. I did have one vendor follow up and ask why we picked another vendor so that he could improve his consultations going forward, but everyone else just said something like "thanks for letting us know and have a great wedding!"